The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Beheading plan sparked police raid: Abbott

A series of anti-terrorism raids were sparked by intelligence reports the Islamic State was planning a public execution in Australia, Prime Minister Tony Abbott says.

Federal and state police executed warrants in Sydney and Brisbane on Thursday which resulted in 15 people being detained and one man charged in Sydney with terrorism-related offences.

Mr Abbott was briefed on the police raid on Wednesday night, which included intelligence that public beheadings were planned.

"The exhortations, quite direct exhortations, were coming from an Australian who is apparently quite senior in ISIL to networks of support back in Australia to conduct demonstration killings here in this country," he told reporters.

"So this is not just suspicion, this is intent and that's why the police and security agencies decided to act in the way they have."

Mr Abbott said Australia was at "serious risk" of a terrorist attack and Australians were supporting extremists who would do the country harm.

"It's important our police and security organisations be one step ahead of them and this morning they were," he said.